Electric meter.



A. G. DA-VIS.

' ELECTRIC METER.

APPLICATION FILED JAN. 13, I913.

Patented Oct. 26, 1915.

Witnesses Mfl.

- rarnnr ALBERT G. DAVIS, 013 SCHENEGTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC METER.

Application filed January 13, 1913.

The object of my invention is to provide a novel and improvedconstruction for readily and accurately adjusting or compensatingelectric meters for friction at starting and at light loads.

My invention is particularly adapted to be employed in connection withelectric meters of the mercury motor type in which a rotatable diskarmature is submerged in mercury contained in a suitable chamber, and Ihave accordingly chosen this type of meter for the purpose ofillustrating and describing my invention. In this type of meter, themercury serves to convey the main load current, or a portion thereofobtained by the usual shunt, to the disk armature, which latter islocated in a magnetic field proportional to the voltage of the circuit.The reaction between this magnetic field and the current passing throughthe disk armature produces rotation of the latter, according to wellknown. and established principles.

In meters of the mercury motor type it is customary to connect thepotential winding to the meter armature in such a manner that all or aportion of the current flowing in the winding also passes through themeter armature. The current which thus flows through both the meterarmature and the potential winding produces a torque upon the, armaturewhich acts to compen sate the meter for friction at starting and atlight loads. This torque may be varied by varying the-current flowingthrough the armature, but since it is desirable that the field set up bythe potential winding be maintained substantially constant it isnecessary to provide means for maintaining this'coIlstant field whilevarying the compensating current flowing through the armature. By myinvention this object is accomplished in a convenient and simple mannerand the meter readily and accurately compensated for friction atstarting and at light loads.

In carrying out my invention I connect Specification of Letters Patent.

Patented Oct. 26, T9115.

Serial No. 741,667.

the potential winding to the armatare circurt 1n such a manner that thecurrent flowmg through the potential winding also flows through thearmature circuit, and I accomplish the object of my invention by theprovision of means for varying the current fiowing in the potentialwinding without substantially. altering the active ampere turns of suchwinding. The novel features which I believe to be characteristic of myinvention. are indicated in the claims appended hereto. The features ofconstruction and mode of operation of a meter embodying my inventionwill be understood from the following description taken in connectionwith the accompanying drawings, in which:

Figure l .is a diagrammatic view of av meter embodying the novelfeatures of my invention and Fig 2 is a modification thereof.

The meter shown in the drawings comprises a casing or receptacle 1 ofinsulating material adapted to contain a quantity of mercury 2. Withinthe casing and sub merged in the mercury is a rotatable disk armature 3secured to a pivoted shaft 4:.

The shaft ticdl'lVES a counter mechanism 5 in the well known manner, andis provided with the usual damping disk 6 operatively located betweenpermanent magnets 7. An

electromagnet 8 has its poles entering the base of the casing 1 at asuitable distance from each side of the center thereof. An iron or steelplate 9 is inserted in the top of the casing 1 and forms a return pathfor the magnetic lines of force proceeding from pole to pole of themagnet S.

The electromagnet is energized by a potential winding or coilconstructed in several sections 10. In series with each section of thiswinding is a resistance 11. Each sec- I tion of the winding, togetherwith its associated resistance, is suitably connected to a dial switch12 in such a manner that a movement of the operating lever of the switchserves to place one or more units of winding and resistance in circuitacross the mains 13, which latter supply current to the load 14 from asuitable source 15. The electromagnet is also provided with a few turnsof a compound series winding 16 connected in series with the armatureand the load. In the drawings a shunt 17 is shown so that -only aportion of the load current passes through the armature and the serieswinding. In order that the current taken by the potential winding mayfiow through the armature a tap is made in the series winding at 18to'which is connected one terminal of the first section of the potentialwinding. The current is conducted to and from the armature by means ofterminals 19 passing through the casing and in contact with the mercurywithin the same.

The operation of my improved friction and light load compensating meansis as follows: The total current passing through the potential windingmust also pass through the meter armature. This current acts tocompensate for the friction of the meter at starting and at light loads.The amount of this current. can be varied by the manipulation of theoperating handle of the switch 12, and thusthe degree or amount ofcompensation can be adjusted. The sections 10 of the potential windingand their respective associated resistances 11 are so proportioned thatthe total ampere turns of the potential winding is substantiallyconstant, for

'a constant terminal voltage, for any position of the switch 12. Thecompensating current flowing through the armature and potential windingin series can thus be varied and adjusted without altering the strengthof the field due to the potential winding.

In Fig. 2 of the drawings I have illustrated a modified construction. Itwill obviously be unnecessary in many cases to divide the entirepotential winding into sections as shown in Fig. 1. In such cases theconstruction shown in Fig. 2 may be employed. In this figure themajor'p'ortion 20 of the potential winding is without taps and only afew of the end turns of the winding are divided into the sections '10.Associated with each section 10 is a resistance 11, and the sections andresistances are connected to the switch 12 as in the constructiondescribed in connection with Fig.1. Bythe construction of Fig. 2 a fineradjustment of the compensating current canbe obtained,- but the totalrange of adjustment is less than with the construction of Fig. 1.

In the construction shown in both Figs. 1 and 2, the properapportionment of the number of turns of the potential winding in eachsection, and of the amount of resistance associated with each sectionisan important condition precedent to the successful opera tion of myinvention. As previously intimated, the number of turns of winding ineach section and the amount of resistance associated therewith are sodetermined that the active ampere turns of the potential winding remainsubstantially constant regardless of the position of the switch 12, andprovided of course that the terminal voltage of the external circuitremains constant.

The ampere turns of the potential winding are thus substantiallyindependent of the number of sections actively included in the circuitof the potential winding. The armature circuit has an appreciableresistance and for this reason it is necessary to employ the resistancesections 11 or 11, as the case may be, in order to maintain the ampereturns substantially constant regardless of the number of actual turnsactively included in the potential winding.

It is'evident that other arrangements of resistances and sections ofpotential winding can be employed other than those which I havespecifically illustrated in, the drawings. I do not wish, therefore, tobe limited to the precise constructions shown and described since manychanges may be made therein withoutdeparting from the spirit of myinvention.

l/Vhat I claim as new and desire to secure by Letters Patent of theUnited States, is

1. An electric meter comprising a receptacle containing mercury, arotatable armature within said receptacle, a potential windingelectrically connected to said armature, means for supplying to saidarmature a friction compensating current, and means for adjusting theamount of said compensating current by varying the current flowing insaid potential winding and for maintaining the field strength due tosaid potential winding substantially constant as the current flowingtherein is varied. I

2. An electric meter comprising a rotatable armature, a potentialwinding electrically. connected to said armature, a resistanceelectrically connected to the potential winding, and means forsimultaneously cutting out a section of the potential winding and asection of the resistance.

3. An electric meter comprising a rotatable armature, a potentialwinding in series with said armature, said potential winding.

having several sections, a resistance in series with each section ofsaid winding, and means for varying the number of sections andassociated resistances actively included in the potential winding.

4. An electric. meter comprising a rotatable armature, a potentialwinding in series with said armature, said potential winding having aplurality of sections, a resistance in series with each section, thenumber of turns of winding in each section and the amount of resistanceassociated therewith being such that the ampere turns of the potentialwinding are substantially independent of the number of sections activelyincluded in the Winding, and means for varying the number of sectionsactively included in the potential winding.

5. An electric meter comprising a rotatable armature, a potentialwinding electrically connected'thereto, a resistance electricallyconnected to said winding, said winding and said resistance beingdivided into operatively associated sections, the number of turns ofWinding and the amount of resistance included'in each section being suchthat the ampere turns of the potential Winding are substantiallyindependent of the number of sections actively included in the winding,and means for varyingthe number of associated sections actively includedin the potential Winding.

6. An electric meter comprising a receptacle containing mercury, arotatabledisk armature Within said receptacle, means for supplyingcurrent to said armature, a potential Winding electrically connected tosaid armature, a resistance electrically connected to said Winding, saidWinding and said resistance being operatively dividedinto associatedsections, the value of the resistance of said sections being such thatthe ampere turns of the potential Winding remain substantially constantregardless of the number of turns actively included in the Winding, andmeans for varying the number of associated sections actively included inthe potential Winding.

In Witness whereof, I have hereunto set my hand this 11th day ofJanuary, 19. 3.

ALBERT G. DAVIS.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

